Police video taken on the day of the Hillsborough disaster contains an “unexplained” 10-minute gap in one of the tapes, it has emerged at a pre-inquest hearing in London on Monday, while some officers have admitted they believe they were pressurised into accepting changes to their statements.

Police video taken on the day of the Hillsborough disaster contains an “unexplained” 10-minute gap in one of the tapes, it has emerged at a pre-inquest hearing in London on Monday, while some officers have admitted they believe they were pressurised into accepting changes to their statements.

Families of the 96 Liverpool fans who died in the tragedy demanded that experts be allowed to analyse the matchday recording, so that the inquest due to be held next year could cover the events “warts and all”.

It has also emerged that Met Commissioner Sir Bernard Hogan-Howe, a former officer with South Yorkshire Police, is to be investigated by the Independent Police Complaints Commission (IPCC) over his role in the disaster.

It follows a complaint by Paul Spearritt, who claims his late brother’s name was wrongly put onto a list of survivors read out by an officer, whom he believes may have been Sir Bernard.

Mr Spearritt also alleged that ensuing statements made by the Commissioner had been misleading. Both matters were referred to the London Mayor’s Office for Policing and Crime before being passed back to the IPCC.

The pre-inquest hearing held at a central London hotel today also heard that 19 former or serving officers had either declined or were yet to respond to interview requests by investigators considering evidence that statements were altered following the crush in 1989.

Pressure is mounting for the names of those that have failed to co-operate with the inquiry to be disclosed, as lawyers for the families also sought details of all 240 officers whose evidence may have been altered to be made public.

The IPCC, which is investigating the handling of the original police inquiry by West Midlands Police, said it was prepared to disclose the names but only to the coroner Lord Justice Goldring.

Relatives of the dead groaned when they heard that a tape recorded by South Yorkshire Police at the match in Sheffield was incomplete.

Pete Weatherby QC, who is representing 22 families from the Hillsborough Justice Campaign, said there was an “an unexplained 10-minute gap" in one of the 20-minute tapes.

A second tape, which was expected to contain continuous footage, was found to be adulterated with film from the first tape.

Mr Weatherby urged the coroner to allow the tapes to be copied and analysed, telling the hearing: “There may be integrity issues here."

Campaigner Margaret Aspinall said: “Where is that 10 minutes? What went on in those 10 minutes? Give us the whole jigsaw, we need it warts and all.”

Rachel Cerfontyne, the deputy chair of the IPCC, said that a number of the 143 officers interviewed so far claimed they had come under pressure to accept changes to their statements, or did so after discussion from senior officers.

Others believed they were being made for legal reasons, or were unaware that changes had been made. A further 47 officers are still awaiting interview, but the remainder have either died, are unfit to be interviewed or have refused to co-operate.

Ms Cerfontyne said that issuing names of those officers publicly could pose a risk to the investigation.

“I understand many will find this disappointing, but I must stress we are not deliberately concealing information. I am determined not to do anything which may undermine the integrity of the investigation,” she added.